This invention relates to material handling apparatus and, more specifically, to material handling apparatus of the type wherein a boom is mounted on a vehicle and which further includes an improved swing motor for swinging the boom relative to the vehicle.
Prior art of possible relevance includes the following United States patents: Gerry et al U.S. Pat. No. 2,765,778; Davis U.S. Pat. No. 3,090,244; Rudd et al U.S. Pat. No. 3,190,190; Rumsey et al U.S. Pat. No. 3,195,421; Drake U.S. Pat. No. 3,215,046; Elliott et al U.S. Pat. No. 3,270,894; and Jackson et al U.S. Pat. No. 3,758,941.
Compactness and reliability through simplicity are and have been highly desirable qualities in material handling apparatus as, for example, in drive systems for booms mounted on vehicles. In vehicle mounted boom apparatus, there is almost universally a requirement that the boom be swingable about a vertical axis relative to the vehicle for positioning purposes. And, it is highly preferred that motor devices employed to swing the boom about such axis function in conjunction with swing pins mounting the boom for such movement on the axis.
Consequently, motors used for the purpose must be compact yet powerful and capable of being fitted within the connection of the boom to the vehicle to operate on such axis.
Moreover, because of such positioning and compactness, it is highly desirable that the motors be simple in construction so as to provide improved reliability by reason of such simplicity.
Typically, the motors employed are hydraulic motors. Because of the numerous and abrupt cyclic movement changes in use, as when the boom mounts a backhoe, they are subject to high fluid pressures and structural stresses. Such loads are cyclically borne by the seals employed with the result that premature wear and failure frequently occurs requiring all too frequent servicing.